This invention relates to a magnetic shielding structure of an analog type electronic timepiece which drives hands through a hand wheel to indicate time, and more particularly relates to a structure integrating a magnetic shielding with an hour wheel supporting of an analog type electronic timepiece.
In conventional timepieces, there has a well known the structure of the magnetic shielding wherein a casing of an exterior is made of a material having a high magnetic permeability or such material is disposed as a separate member on the outer peripheral side of a coil block.
However, if a casing ring is composed of a magnetic screen, the casing ring becomes complicated in shape and becomes an expensive component. And if the magnetic screen is disposed outside the coil block, a movement becomes greater in size due to the thickness of the magnetic screen, and this renders the problem in that the timepiece cannot be made compact.
On the other hand, in timepieces having the structure wherein only an hour wheel is interposed between a main plate and a dial, an hour wheel friction spring made of a thin spring plate and an hour wheel seat, if necessary, are disposed on a shaft of the hour wheel between the hour wheel and the dial in order to secure and adjust vertical clearance of the hour wheel.
However, if the hour wheel friction spring and the hour wheel seat are disposed between the hour wheel and the dial, the force of the hour wheel friction spring for providing the vertical clearance of the hour wheel acts on the hour wheel and consequently, braking force is always applied to the hour wheel. This is one of the factors which reduces efficiency of the hand operation torque. Moreover, if the dial is removed for repair, at the time of repair the dial is usually detached for prevent a damage of the surface thereof , the hour wheel, the hour wheel friction spring and the hour wheel seat come also off and particularly because the hour wheel friction spring and the hour wheel seat are extremely small, they are often lost. If at least one of the hour wheel and the minute wheel is made of plastic material, the plastic component is often damaged when the hour wheel or the like is assembled again after the end of repair.